US2005/0021181 discloses a robot cleaner comprising such a device, wherein the body is motor-driven to move the robot cleaner across a surface. A semicircular ring-shaped bumper for mitigating shocks caused by sudden collisions with unexpected obstacles is attached to the body. The bumper is movable with respect to the body in one predetermined direction.
However, when a robot cleaner is moved across a surface, obstacles may be located anywhere so that the direction of impact may be in any direction parallel to the surface across which the robot cleaner is being moved.
Impact in a direction not parallel to the direction in which the bumper is movable with respect to the body may still cause damage to the body.
Such problems do not only occur with robot cleaners but also with other, motor-driven or manually driven devices that are movable across a surface.
Furthermore, the robot cleaner according to US-A1-2005/0021181 needs special guiding elements so as to guide the movement of the bumper with respect to the body.